1. Field of Invention
The present invention is directed to an LCD (liquid crystal display) power supply. More particularly, the present invention provides an LCD power supply for driving a CCFL (Cold Cathode Fluorescent Lamp).
2. Description of Related Art
FIG. 1 depicts a conventional LCD power supply system for driving a CCFL 150. The system includes an AC to DC circuit 120, a DC to AC circuit 130, and a transformer 140. The AC to DC circuit 120 is coupled to the AC input source 110 to provide a DC voltage. The DC to AC circuit 130 couples the DC voltage to a primary side of the transformer 140 and alternative polarities thereof. A CCFL 150 is coupled to a secondary side of the transformer 140. Hence, the secondary side of the transformer 140 generates an AC signal to supply to the CCFL 150.
Moreover, the conventional LCD power supply system further includes a feedback circuit 160 configured between the CCFL 150 and the DC to AC circuit 130. The feedback circuit 160 receives a feedback signal from the CCFL 150 to generate a modulation signal. The modulation signal is transmitted to the DC to AC circuit 130 and modulates a time parameter indicative of the DC voltage coupling time with the primary side of the transformer 140. Hence, the DC to AC circuit 130 couples the DC voltage to the primary side of the transformer 140 with a variable duty cycle according to the modulation signal. Therefore, the transformer 140 is based on the modulation signal to deliver power to the CCFL 150 load.
However, a new power supply system for driving CCFL is still needed as an alternative option for the wide application of the LCD.